The present invention relates generally to fuel systems for internal combustion engines, and more specifically to such systems including one or more fuel pumps responsive to one or more corresponding pump actuation signals to supply high pressure fuel to associated fuel collection units.
In recent years, advances in fuel systems for internal combustion engines, and particularly for diesel engines, have increased dramatically. However, in order to achieve optimal engine performance at all operating conditions with respect to fuel economy, exhaust emissions, noise, transient response, and the like, further advances are necessary. As one example, operational accuracy with electronically controlled fuel systems can be improved by providing for fast and accurate control of fuel injection pressure independent of engine timing, engine speed and engine load.
Heretofore, conventional electronic fuel pressure control systems have employed known control techniques, including open or closed loop strategies, for controlling the operation of high pressure fuel pumps and, in turn, fuel injection pressure. However, while some such techniques have been designed to control fuel pressure under both steady state and transient operating conditions to therefore provide for the ability to quickly and accurately modify fuel injection pressure, no such control techniques are known that further provide for compensation of engine-to-engine (i.e., between-engine) variations in operating parameters as well as system non-linearities. Moreover, no fuel pressure control systems are known wherein such control techniques are adaptively adjustable to thereby maintain accuracy under all engine and fuel system operating conditions including controllable factors such as engine timing, fuel quantity, and the like, and typically uncontrollable factors (i.e., noise factors) such as environment, deterioration, duty cycle, and the like. What is therefore needed is an improved fuel injection pressure control strategy operable to control fuel pump operation under both steady state and transient conditions to thereby provide for fast and accurate control of fuel injection pressure, and to furthermore adaptively adjust such fast and accurate fuel pump control to thereby compensate for between-engine operating parameter variations as well as system non-linearities.
The foregoing shortcomings of the prior art are addressed by the present invention. In accordance with one aspect of the present invention, a fuel injection pressure control system for an internal combustion engine comprises a fuel pump responsive to a fuel pump command to supply pressurized fuel, means responsive to at least a desired injection pressure for determining the fuel pump command as a function thereof, and means responsive to at least a desired injection pressure and the fuel pump command for revising the function.
In accordance with another aspect of the present invention, a fuel injection pressure control system for an internal combustion engine comprises a fuel pump responsive to a fuel pump command to supply pressurized fuel, means for determining an injection pressure corresponding to a pressure of fuel supplied by the fuel pump and dispensed into a combustion chamber of an internal combustion engine, means for producing an initial fuel pump command, means responsive to the desired injection pressure and the injection pressure for determining a fuel pump adjustment command based on a predefined control strategy, means responsive to the injection pressure and the fuel pump command for revising at least one control parameter of the predefined control strategy, and means for producing the fuel pump command as a function of the initial fuel pump command and the fuel pump adjustment command.
In accordance with yet another aspect of the present invention, a fuel injection pressure control system for an internal combustion engine comprises a fuel pump responsive to a fuel pump actuation signal to supply pressurized fuel, means for determining an injection pressure corresponding to a pressure of fuel supplied by the fuel pump and dispensed into a combustion chamber of an internal combustion engine, and a control circuit including a closed-loop control strategy producing a first control signal as a function of a difference between the injection pressure and a desired injection pressure value and an open-loop control strategy producing a second control signal as a function of at least the desired injection pressure value, the control circuit producing the fuel pump actuation signal as a function of the first and second control signals.
In accordance with a further aspect of the present invention, a method for controlling fuel injection pressure in an internal combustion engine comprises the steps of determining an injection pressure corresponding to a pressure of fuel dispensed into a combustion chamber of an internal combustion engine, producing an initial fuel pump command as a function of at least one control parameter of an open-loop control strategy, producing a fuel pump adjustment command as a function of at least one control parameter of a closed-loop control strategy, producing a fuel pump command as a function of the initial fuel pump command and the fuel pump adjustment command, the fuel pump command controlling operation of a fuel pump supplying fuel for dispensing into the combustion chamber, updating the at least one control parameter of the open-loop control strategy as a function of at least a desired injection pressure and the fuel pump command, and updating the at least one control parameter of the closed-loop control strategy as a function of the injection pressure and the fuel pump command.
One object of the present invention is to provide an improved strategy for controlling fuel injection pressure in an internal combustion engine.
Another object of the present invention is to provide such an improved strategy by controlling the operation of a fuel pump operable to supply high pressure fuel for subsequent dispensing into a combustion chamber of the engine.
Yet another object of the present invention is to provide such an improved strategy by combining closed loop and open loop strategies to thereby control both steady state and transient operating conditions.
Still another object of the present invention is to provide such an improved strategy by adaptively adjusting the closed loop and open loop control parameters to thereby compensate for between-engine operating parameter variations as well as system non-linearities.
These and other objects of the present invention will become more apparent from the following description of the preferred embodiments.